Method for manufacturing a diaphragm for a gasmeter

Abstract

This method for forming a measuring diaphragm which measures the volume of a passing gas with high accuracy and has a prolonged service life because the diaphragm moves completely in the same way to both sides of the measuring vessel in which it is fixed. The measuring diaphragm when produced in quantity has an undulating structure of high uniformity and variation in quality of the diaphragm is small. The method of preparation of the measuring diaphragm includes providing each of a pair of molds with a flat part at the center and providing a multiplicity of grooves and ribs at the periphery parallel to an edge of the central part; placing the grooves and ribs in such a way that the grooves of one mold fit the ribs of the other mold, such that the depth of a groove on a mold is larger than the height of a rib on the other mold which fits the groove; pressing an elastomer composite sheet material between the molds, such that one side of the pressed elastomer composite sheet material is pressed to the surface of the ribs of the mold and fixed there with tension and the other side of the elastomer composite sheet material is out in contact with the surface of the grooves of the mold; and then heating the elastomer composite sheet material to crosslink the elastomers composite sheet and to form a desired shape.

What is claimed is: 
     
       1. In a method for manufacturing a flexible unitary measuring diaphragm to have little or no residual strain therein, for use in gasmeters, the steps comprising: providing a first mold and a second mold to form said diaphragm;   forming each of said molds to have: a central portion, said central portion of each mold having a predetermined shaped edge portion, a flat center, a length and a width; and   a plurality of alternating grooves and ribs surrounding said central portion of each mold, said grooves and ribs being formed to be parallel to the predetermined shaped edge portion of the central portion of each mold;   a smaller one of the length and the width of said central portion of each mold having a first dimension when measured along a straight line extending through the center of the central portion of each mold to a point on said edge portion of said central portion of each mold, that is a multiple, greater than one, of a second dimension that is a dimension of one of the ribs and a groove adjoining the one rib as measured along said straight line when said straight line is extended to a respective edge of each of said molds; and     arranging the grooves and ribs on the molds so that respective ribs of each mold fit into respective corresponding grooves of the other mold when the molds are pressed together in an operational position;   adjusting a depth of the grooves on each of the molds so that a bottom portion of each groove is separated by a given space from the rib fitting thereinto when said molds are in said operational position;   positioning between said molds without tightly fixing to said molds, an elastomer composite sheet material having a first and a second surface;   pressing the molds together with the not tightly fixed elastomer composite sheet material therebetween, so that the elastomer composite sheet material is pressed on both said first and second surfaces thereof and is held by said central portions of each of the molds and fits over and adheres by tension to a surface of each of the ribs of the molds while being spaced apart from the bottom portion of each of the grooves, by a second space smaller than said given space;   the elastomer composite sheet material being drawn by each of said ribs of said molds at not tightly fixed portions of said elastomer composite sheet as said molds are pressed together to be in said operational position;   the respective second spaces separating bottom walls of each of the grooves from the stretched elastomer composite sheet material which contacts a respective facing rib, thereby providing a uniform stress distribution in the first and second surfaces of the drawn elastomer composite sheet material;   said molds providing a central portion in said elastomer composite sheet material which is pressed on both said first and second surfaces thereof by the molds; and   then heating the drawn elastomer composite sheet material to crosslink said material while the drawn elastomer composite sheet material adheres to the ribs of the molds, thereby to form said measuring diaphragm having little or no residual strain therein with said central portion surrounded by alternating ribs and grooves.   
     
     
       2. The method according to claim 1, comprising: forming the plurality of grooves and ribs surrounding said central portion of said molds with continuous half circularity.   
     
     
       3. The method according to claim 1, wherein the elastomer composite sheet material is heat shrinkable, the heating step comprises heat shrinking said elastomer composite sheet material. 
     
     
       4. The method according to claim 1, further comprising the additional steps of: providing an outer edge portion on each of said molds which surrounds the plurality of alternating grooves and ribs, said outer edge portion of each mold having substantially the same shape and being substantially parallel to the edge portion of said central portion of each mold.   
     
     
       5. The method according to claim 1, comprising the additional steps of: removing the diaphragm from the molds after the heating step; and   mounting the thus formed diaphragm in a frame.   
     
     
       6. The method according to claim 1, wherein the step of positioning said elastomer composite sheet material comprises positioning a lamination of a flexible plastics film and a rubber coated fabric between said molds. 
     
     
       7. The method according to claim 1, wherein the step of positioning said elastomer composite sheet material comprises positioning a fabric coated with an elastomer between said molds. 
     
     
       8. The method according to claim 6, wherein the lamination comprises said flexible plastics film laminated to an epichlorhydrin rubber and a hundred denier plain fabric. 
     
     
       9. The method according to claim 1, wherein the step of positioning said elastomer composite sheet material comprises positioning a lamination of a flexible plastics film, an epichlorhydrin rubber and a hundred denier plain fabric between said molds. 
     
     
       10. The method according to claim 1, wherein the step of positioning the elastomer composite sheet material comprises positioning a sheet material comprising an epichlorhydrin rubber and a hundred denier plain fabric between said molds. 
     
     
       11. In a method for manufacturing a flexible unitary measuring diaphragm to have little or no residual strain, for use in gasmeters, the steps comprising: providing a first mold and a second mold to form said diaphragm;   forming each of said molds to have: a central portion, said central portion of each mold having a predetermined shaped edge portion, a flat center, a length and a width; and   a plurality of alternating grooves and ribs surrounding said central portion of each mold, said grooves and ribs being formed to be parallel to the predetermined shaped edge portion of the central portion of each mold;   a smaller one of the length and the width of said central portion of each mold having a first dimension when measured along a straight line extending through the center of the central portion of each mold to a point on said edge portion of said central portion of each mold, that is a multiple, greater than one, of a second dimension that is a dimension of one of the ribs and a groove adjoining the one rib as measured along said straight line when said straight line is extended to a respective edge of each of said molds; and     arranging the grooves and ribs on the molds so that respective ribs of each mold fit into respective corresponding grooves of the other mold when the molds are pressed together in an operational position;   adjusting a depth of the grooves on each of the molds so that a bottom portion of each groove is separated by a given space from the rib fitting thereinto when said molds are in said operational position;   positioning between said molds without tightly fixing to said molds, an elastomer composite sheet material having a first and a second surface;   said elastomer composite sheet material being formed by laminating a flexible plastic film to a rubber coated fabric;   pressing the molds together with the not tightly fixed elastomer composite sheet material therebetween, so that the elastomer composite sheet material is pressed on both said first and second surfaces thereof and is held by said central portions of each of the molds and fits over and adheres by tension to a surface of each of the ribs of the molds while being spaced apart from the bottom portion of each of the grooves, by a second space smaller than said given space;   the elastomer composite sheet material being drawn by each of said ribs of said molds at not tightly fixed portion of the elastomer composite sheet as said molds are pressed together to be in said operational position;   the respective second spaces separating bottom walls of each of the grooves from the drawn elastomer composite sheet material which contacts a respective facing rib, thereby providing a uniform stress distribution in the first and second surfaces of the drawn elastomer composite sheet material;   said molds providing the central portion in said elastomer composite sheet material which is pressed on both said first and second surfaces thereof by the molds; and   then heating the drawn elastomer composite sheet material to crosslink said material while the drawn elastomer composite sheet material adheres to the ribs of the molds, thereby to form said measuring diaphragm having little or no residual strain therein with said central portion surrounded by alternating ribs and grooves.   
     
     
       12. The method according to claim 11, wherein the elastomer composite sheet material comprises an epichlorhydrin rubber and a hundred denier plain fabric. 
     
     
       13. The method according to claim 11, wherein the elastomer composite sheet material is heat shrinkable, the heating step comprises heat shrinking said elastomer composite sheet material. 
     
     
       14. The method according to claim 11, further comprising the additional steps of: providing an outer edge portion on each of said molds which surrounds the plurality of alternating grooves and ribs, said outer edge portion of each mold having substantially the same shape and being substantially parallel to the edge portion of said central portion of each mold.   
     
     
       15. The method according to claim 11, comprising the additional steps of: removing the diaphragm from the molds after the heating step; and   mounting the thus formed diaphragm in a frame.   
     
     
       16. In a method for manufacturing a flexible unitary measuring diaphragm to have little or no residual strain, for use in gasmeters, the steps comprising: providing a first mold and a second mold to form said diaphragm;   forming each of said molds to have: a central portion, said central portion of each mold having a predetermined shaped edge portion, a flat center, a length and a width; and   a plurality of alternating grooves and ribs surrounding said central portion of each mold, said grooves and ribs being formed to be parallel to the predetermined shaped edge portion of the central portion of each mold;   a smaller one of the length and the width of said central portion of each mold having a first dimension when measured along a straight line extending through the center of the central portion of each mold to a point on said edge portion of said central portion of each mold, that is a multiple, greater than one, of a second dimension that is a dimension of one of the ribs and a groove adjoining the one rib as measured along said straight line when said straight line is extended to a respective edge of each of said molds; and     arranging the grooves and ribs on the molds so that respective ribs of each mold fit into respective corresponding grooves of the other mold when the molds are pressed together in an operational position;   adjusting a depth of the grooves on each of the molds so that a bottom portion of each groove is separated by a given space from the rib fitting thereinto when said molds are in said operational position;   positioning between said molds without tightly fixing to said molds, an elastomer composite sheet material having a first and a second surface;   said elastomer composite sheet material being formed by coating a fabric with an elastomer;   pressing the molds together with the not tightly fixed elastomer composite sheet material therebetween, so that the elastomer composite sheet material is pressed on both the first and second surfaces thereof and is held by said central portions of each of the molds and fits over and adheres by tension to a surface of each of the ribs of the molds while being spaced apart from the bottom portion of each of the grooves, by a second space smaller than said given space;   the elastomer composite sheet material being drawn by each of said ribs of said molds at not tightly portion of the elastomer composite sheet as said molds are pressed together to be in said operational position;   the respective second spaces separating bottom walls of each of the grooves from the drawn elastomer composite sheet material which contacts a respective facing rib, thereby providing a uniform stress distribution in the first and second surfaces of the drawn elastomer composite sheet material;   said molds providing a central portion in said drawn elastomer composite sheet material which is pressed on both said first and second surfaces thereof by the molds; and   then heating the drawn elastomer composite sheet material to crosslink said material while the drawn elastomer composite sheet material adheres to the ribs of the molds, thereby to form said measuring diaphragm having little or no residual strain therein with said central portion surrounded by alternating ribs and grooves.   
     
     
       17. The method according to claim 16, wherein the elastomer composite sheet material comprises an epichlorhydrin rubber and a hundred denier plain fabric. 
     
     
       18. The method according to claim 16, wherein the elastomer composite sheet material is heat shrinkable, the heating step comprises heat shrinking said elastomer composite sheet material. 
     
     
       19. The method according to claim 16, further comprising the additional steps of: providing an outer edge portion on each of said molds which surrounds the plurality of alternating grooves and ribs, said outer edge portion of each mold having substantially the same shape and being substantially parallel to the edge portion of said central portion of each mold.   
     
     
       20. The method according to claim 16, comprising the additional steps of: removing the diaphragm from the molds after the heating step; and   mounting the thus formed diaphragm in a frame.